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This study examines the climate response to a sea surface temperature (SST) warming imposed over the southwest tropical Indian Ocean (TIO) in a coupled ocean–atmosphere model. The results indicate that the southwest TIO SST warming can remotely modulate the atmospheric circulation over the western North Pacific Ocean (WNP) via interbasin air–sea interaction during early boreal summer. The southwest TIO SST warming induces a "C shaped" wind response with northeasterly and northwesterly anomalies over the north and south TIO, respectively. The northeasterly wind anomalies contribute to the north TIO SST warming via a positive wind–evaporation–SST (WES) feedback after the Asian summer monsoon onset. In June, the easterly wind response extends into the WNP, inducing an SST cooling by WES feedback on the background trade winds. Both the north TIO SST warming and the WNP SST cooling contribute to an anomalous anticyclonic circulation (AAC) over the WNP. The north TIO SST warming, WNP SST cooling, and AAC constitute an interbasin coupled mode called the Indo-western Pacific Ocean capacitor (IPOC), and the southwest TIO SST warming could be a trigger for IPOC. While the summertime southwest TIO SST warming is often associated with antecedent El Niño, the warming in 2020 seems to be related to extreme Indian Ocean dipole during the autumn of 2019. The strong southwest TIO SST warming seems to partly explain the strong summer AAC of 2020 over the WNP even without a strong antecedent El Niño. [ABSTRACT FROM AUTHOR]

Westerly wind bursts play an important role in the development of El Niño-Southern Oscillation (ENSO) events. However, the impact of easterly wind bursts (EWBs) on the development of ENSO is still unclear. In particular, a series of strong EWBs in the summer of 2014 aroused arguments about their importance in suppressing the potential warming in the summer. In this study, we conduct a series of sensitivity experiments using the fully-coupled NCAR Community Earth System Model with prescribed strong EWBs to distinguish their impact on the development of the model El Niño events, as well as the seasonality of the potential impact. Model results indicate that wintertime warming is significantly suppressed by the EWBs in summer due to the strongest ocean–atmosphere interaction associated with the most unstable background coupled system. With stronger anomalous zonal SST gradient and relatively more stable background state, the EWB-induced cooling in autumn is smaller than the cooling induced by the summertime EWBs. In spring when the ocean–atmosphere interaction is relatively weaker, the impact of EWBs depends on the EWB-forced shift of the eastern edge of warm pool (EEWP), which is critical for the establishment of positive Bjerknes feedback. A mixed layer heat budget analysis further suggests that the seasonally-dependent impact of EWBs is mainly controlled by the zonal advective feedback process associated with the subsequent ocean–atmosphere interaction and to some extent related to the thermocline feedback as well. This study demonstrates that EWBs increase the uncertainty of the prediction of ENSO initialized in boreal spring and early summer even if the ocean subsurface precursors are strong. [ABSTRACT FROM AUTHOR]

Extensive research has improved our understanding and forecast of the occurrence, evolution and global impacts of the El Niño–Southern Oscillation (ENSO). However, ENSO changes as the global climate warms up and it exhibits different characteristics and climate impacts in the twenty-first century from the twentieth century. Climate models project that ENSO will also change in the warming future and have not reached an agreement about the flavor, as to the intensity and the frequency, of future ENSO conditions. This article presents the conventional view of ENSO properties, dynamics and teleconnections, and reviews the emerging understanding of the diversity and associated climate impacts of ENSO. It also reviews the results from investigations into the possible changes in ENSO under the future global-warming scenarios. [ABSTRACT FROM AUTHOR]

In this study, El Niño events are classified as long El Niño (LE) events and short El Niño (SE) events based on their durations, and the characteristics of the early stages of these events are investigated. Results indicate that LE events tend to start earlier compared to SE events, initiating in boreal spring and peaking in winter. Their early occurrence is attributed to the western equatorial Pacific (WEP) sea surface wind anomalies that benefit the eastward propagation of warmwater by forcing the downwellingKelvin waves. It is also found that the wind anomalies are potentially induced by the convection anomalies over the WEP in spring. Experiments with a fully coupled climate model forced by convection heating anomalies over theWEP show that El Niño events become stronger and longer after introducing anomalous convection heating. The convection anomalies induce an extensive anomalous westerly belt over the WEP, which charges El Niño by eastward-propagating Kelvin waves. Moreover, induced by the anomalously northward-shifted ITCZ heating and the suppressed heating over the Maritime Continent, the equatorially asymmetric westerly belt reduces the meridional shear of mean easterly wind in the lower latitudes, which maintains an anomalous equatorward Sverdrup transport and in turn prolongs the persistence of ElNiño events.Acase study of the 2015/16 superElNiño and a regression study by using a rainfall index in critical regions support the above results. [ABSTRACT FROM AUTHOR]